[mythtv-users] OT: Hybrid drives in a RAID?

[Gary Buhrmaster]

On Wed, Aug 20, 2014 at 1:47 PM, Matt Emmott <memmott at gmail.com> wrote:
.....
>>Because current drives are not designed for multi-drive vibrations, they
>> have not been tested >with RAID 5, 6, or 10, and are not recommended.
>
> I'm going to ignore the last part about multi-drive vibrations because I
> assume it's some CYA warranty fluff, and danger is my middle name. But, I
> don't know what I don't know

Multi-drive vibrations can be a significant source of soft errors
on drives.  I cannot quickly locate the research papers on the
topic, but the backblaze blogs covered it too.  Systems (such
as your PowerEdge) quality drives to minimize the failures.
All the disk vendors have drives explicitly qualified for multi-drive
environments that have advanced vibration resistance to
mitigate the impact.  Consumer drives have gotten better
(as they share many components/design criteria with their
enterprise brethren).  Any particular model will vary.

<conjecture>
Since I have not actually run tests to provide statistically
significant measurements, it is my guess that SSHDs,
used only for recording/playback drives, are not likely to
see the 70% performance improvements, since an 8GB
cache is no where near large enough to contain your
content library, which is mostly streamed sequentially.
There may be a small improvement in (filesystem)
metadata access.
</conjecture>